Love the One You're With

I get Nicole's pattern with men, but on the one hand we're supposed to believe she's matured and ready to finally settle down with one person. At least that's how she's portrayed it to me. But she can't even keep to Brady and their "family" when she's with Eric. Yes, I do believe Eric was the one great love for her, but then wasn't Daniel supposed to be that too? Someone young would go running off to the center to be with Eric, but at her age I would expect Nicole to stay away and make a better effort to commit to Brady and understand his concern. It seems he has every right to be so.
But then would this be happening if Ari were not leaving?